It is commonly necessary to utilize an imaging apparatus in order to input paper file information into a computer. The imaging apparatus is, for example, a traditional scanning imaging apparatus, such as a flatbed scanner, a drum scanner and so on. When the traditional scanning imaging apparatus is used, since the paper file (i.e. scanning object) is fixed on a scanning plane flatly and individual corners of the paper file (i.e. scanning object) are fixed and determinate with respect to an image sensor of the traditional scanning imaging apparatus, there is substantially no distortion and deformation in the image obtained by the traditional scanning imaging apparatus. Furthermore, with the development in the technology, there appears some curved surface imaging apparatuses such as a digital camera and a overhead scanner. When the curved surface imaging apparatus is used, for example when the digital camera or the overhead scanner is used to image, in an inclined angle, an opened thick book such as a dictionary, an encyclopedia, a manual or the like, there appears perspective transformation distortion and deformation resulting from perspective transformation in the obtained image due to imaging the opened thick book from above in the inclined angle. Moreover, since the paper face of the opened thick book may curve, there may also appear distortions and deformations such as stretch, compression or the like in the obtained image. Therefore, when the curved surface imaging apparatus is used, it is necessary to correct the obtained distortion and deformation image so as to generate a image without distortions and deformations.
To correct the distortion and deformation image, there is a content-based method of which the basic principle is first to search for text lines or lines in the paper file, and then to estimate the obtained distortion and deformation image according to the searched text lines or lines. However, the content-based method has a disadvantage in that it has many requirements on the contents of the paper file, for example, it requires that there is sufficient information such as text lines, lines or the like in the paper file. Accordingly, if contents in the paper file are mainly pictures and the like while there are less text lines or lines, then the correction effect of the content-based method is poor or even no correction can be achieved.